Sulfide bearing rocks in waste dumps, spent copper heap leach piles, ore stock piles, pit walls, coal spoil and dewatered tailings storage facilities can be long-term sources of water contamination. Sulfides, when exposed to oxygen and water, oxidise to produce sulfates and acid.
Under acid conditions a wide range of metals are more soluble. The resulting leachate is known by several terms, including acid and metalliferous drainage, acid rock drainage and acid mine drainage. Sometimes, interactions with rock neutralise acid. The resulting solution, though pH neutral, may contain high concentrations of dissolved solutes, e.g., sulfate and some metals.
In many instances, acid and metalliferous drainage have high level negative impacts on the environment and require high cost and long-term remediation and treatment measures.
SRK has extensive global experience in assessing the quantification of sulfate production rates, the prediction of leachate geochemistry, and the effects on receiving waters. We have also designed strategies to control the development of sulfide oxidation and have established methods to measure the effectiveness of the control strategies for clients.
Identifying the presence of sulfides in various waste rock types and ore across the deposit, on a sound statistical basis during exploration, and incorporating the management of sulfides into the early overall mine plan provides the best opportunity to meet regulatory and local community expectations, while maintaining control over water management costs.
